Planner personal plan bucket deletion inconsistent across tenants

Hello, we are seeing inconsistent behavior when deleting buckets in Microsoft Planner personal plans and would like to confirm whether this is an expected limitation or a known issue. In a Planner personal plan that is not connected to Microsoft Teams or a Microsoft 365 Group, tasks can be deleted successfully but buckets cannot be deleted and return a 403 Forbidden error even when the DELETE request includes a valid If-Match header with the latest odata etag value. The same scenario works correctly in other tenants where bucket deletion in personal plans succeeds using the same API calls and permissions. We have confirmed that this issue is not related to retention policies such as Microsoft Purview because bucket deletion works in group based plans when performed by a Global Administrator. It is also not related to GPO or Intune policies, and the request format and permissions have been validated by testing both as the plan creator and as a Global Administrator. Based on this behavior, bucket deletion in Planner personal plans appears to behave differently depending on the tenant even when the scenario and permissions are the same. Could you please confirm whether bucket deletion in Planner personal plans is officially supported, whether this tenant specific behavior is an expected design limitation, whether this is a known issue that can be escalated as a bug, and whether there are any recommended approaches for managing or cleaning up personal plans in enterprise environments. Thank you. 

(403 Forbidden)